Apparatus for forming a catheter

ABSTRACT

A catheter assembly including a plastic tube having a cup-shaped bulb at one end and which is oval in cross section. The walls of the bulb are thicker than the remainder of the tube and a hub is molded about the bulb both interiorly and exteriorly thereof. The bulb is formed by placing the tube on a mandrel, which extends from a mandrel carrier, and thereafter placing the carrier on a base so that the upper end of the tube and mandrel extend through a slot and into a heating cavity defined by a housing. The upper end of the tube is subjected to radiant heat on opposite sides thereof to heat the circumference of the tube unevenly to form and define the cup-shaped bulb. The upper end of the tube is heated to a temperature close to its melting point.

This application is a Divisional of application Ser. No. 743,038, filedNov. 18, 1976, now U.S. Pat. No. 4,095,598.

This invention relates to a catheter assembly and to the method andapparatus for making a catheter assembly. Catheters are utilized in thepractice of medicine to establish fluid communication with the veinsand/or arteries of the human body. Catheters typically include a plastictube with a plastic hub molded about one end of the tube. Thedisposition of the hub about one end of the tube is presented problemswith the prior art catheters. Various schemes have been utilized forconnecting the tube to the hub; however, these prior art schemes havenot proved entirely satisfactory. In some instances the pull-offstrength is not sufficient, the pull-off strength being the forcenecessary to pull or separate the tube from the hub. In other words, theconnection between the tube and the hub is frequently not strong enough.Another problem is the occurrence of fluid leakage between the end ofthe tube and the hub at the connection between the tube and the hub.Somewhat ancillary to these problems is the fact that in many prior artassemblies the tube and the hub are allowed to rotate relative to oneanother.

Included in the various schemes utilized to connect the tube to the hubportion are multi-part systems such as a collar or sleeve insertedwithin the end of the tube to force the tube outwardly into engagementwith the hub, deformation of the end of the tube to provide a mechanicallock with the hub as the hub is molded thereabout, etc. There is,however, no prior art system which is sufficiently effective inovercoming the problems of pull-off strength, leakage and relativerotation between the hub and the tube.

Accordingly, the subject invention provides a catheter assembly whichovercomes the problems associated with the prior art in that it includesa plastic tube having an irregular end with the hub disposed about andcontiguous with both the interior and exterior of the irregular end,thereby increasing the pull-off strength to the extent that the tubewill break before it may be separated from the hub while at the sametime preventing leakage between the tube and the hub.

In a more specific sense, the irregular end of the tube is shaped as abulb which is oval, as viewed in cross section, and has walls thickerthan the walls of the tube.

The irregular end of the tube is formed by placing a tube on a verticalmandrel and heating only the end portion of the tube until it increasesin diameter to form the bulb. The apparatus utilized for forming thetube includes means for supporting the plastic tube and heating meansfor radiantly heating the heat zone for heating a predetermined lengthof the end portion of the plastic tube.

Other advantages of the present invention will be readily appreciated asthe same becomes better understood by reference to the followingdetailed description when considered in connection with the accompanyingdrawings wherein:

FIG. 1 is a side elevational view partially broken away and in crosssection of a preferred apparatus for forming the tube utilized in thecatheter assembly of the subject invention.

FIG. 2 is a cross-sectional view taken substantially along line 2--2 ofFIG. 1;

FIG. 3 is a fragmentary cross-sectional view of a tube formed inaccordance with the subject invention;

FIG. 4 is a view taken substantially along line 4--4 of FIG. 3; and

FIG. 5 is an enlarged cross-sectional view showing a mold cavity withthe tube disposed therein in a first position and a mold cavity in asecond position with the hub portion molded about the end of the tube todefine a catheter assembly constructed in accordance with the subjectinvention.

An apparatus for forming a plastic tube for use in the catheter assemblyof the subject invention is generally shown at 10 in FIGS. 1 and 2.

The apparatus 10 includes a means comprising a plurality of verticallydisposed mandrels 12 for supporting the plastic tubes 14. The apparatusalso includes a mandrel carrier means defined by the carrier bar 16 andindividual mandrel supports 18. The mandrel carrier bar 16 is manuallymovable into and out of the apparatus 10. Specifically, the apparatus 10includes a base or base means 20 including the positioning blocks 22 andstop means 24 for receiving and positioning the carrier bar 16. The stopmeans 24 includes a threaded adjusting screw threadedly engaging abracket to longitudinally align the position of the mandrel carriermeans 16.

The apparatus 10 also includes heating means for radiantly heating aheat zone for heating a predetermined length of the end of the plastictubes 14. More specifically, the heating means includes the housingmember 26 which defines a pair of spaced top and bottom walls 28 and 30,respectively. The top and bottom walls 28 and 30 extend generallyperpendicular to the mandrels 12. The top wall 28 extends across the topof the mandrels 12 and the bottom wall 30 includes a slot defined by thelips 32 for receiving and through which the upper ends of the mandrels12 extend. The member 26 is supported upon the base 20 by threadedsupport posts 27 which have threaded nuts thereon respectively engagingthe member 26 and the base 20 for adjusting the vertical position of themember 26 relative to the base 20.

The heating means also includes the heat generating means comprising theheat generating devices defined by the electrical resistance heaters 34.The heaters 34 are disposed between the top and bottom walls 28 and 30and are spaced inwardly from the edges of the slot defined by the lips32 whereby the heaters 34 are spaced laterally from the ends of themandrels 12. The slot defined by the lips 32 is elongated and extendsfrom one end of the member 26 to the other. Insulating members 36 aredisposed at each end of the member 26 to close the ends of the slot forretaining the heat generated within the chamber or cavity definedbetween the top and bottom walls 28 and 30. It will be appreciated thatthe insulating member 36 on the left end, as viewed in FIG. 1, isremovable for inserting and removing the mandrels 12 into and out of themember 26. It will be appreciated that the member 26 defines a generallyrectangular chamber or cavity, as viewed in cross section, with thebottom of the rectangle having a slot extending therealong for receivingthe ends of the mandrels 12. The extreme or lateral ends of therectangle shape support the heating devices 34 which provide radiantheat subjected to opposite sides of the tubes disposed on the mandrels12. The lips 32 also define shields which prevent the heat from beingsubjected to portions of the tubes other than the extreme end portions,i.e., the predetermined length at the end of each tube which is to beformed into the shape of a cup-shaped bulb.

While the carrier means 16 is removed from the apparatus 10, plastictubes 14 are disposed upon the mandrels 12. Thereafter the carrier means16 is disposed on the base member 20 in a position as determined by theguide members 22 and the stop means 24 whereby the predetermined lengthsof the upper ends of the tubes 12 are disposed in the heating chamberwith the remaining portions of the tubes shielded by the lips 32 fromthe heat generated in the heating chamber or cavity. The end portion ofthe tubes are radiantly heated to a temperature which approaches themelting point of the plastic of the tube which, in the preferredembodiment, is a temperature of between 675° F. and 700° F. and for aperiod of approximately 15 seconds. The plastic tubes 14 remain on thevertically disposed mandrels 12 with their upper ends subjected to theradiant heat until the predetermined length of the end of each tubeincreases in diameter to form a cup-shaped bulb which has a wallthickness greater than the wall thickness of the remaining portion ofthe tube Specifically, such cup-shaped bulbs are shown at 40.

Since the heating member 26 is elongated and the heating devices 34extend therealong on opposite sides of the tubes 14, the opposite sidesor portions of the circumference of the tubes 14 are heated differentlythan the remaining circumference of the tubes. In other words, oppositesides of the tubes 14 are heated differently or at a higher rate and aresubjected to a higher temperature than the remainder of thecircumference of the upper ends of the tube to define an oval-shapedbulb, as viewed in cross section or as viewed in a direction generallyparallel to the axis of each tube 14. Such an oval configuration isshown in FIG. 4.

Once the upper end of a tube is formed into the cup-shaped bulb, asillustrated in FIGS. 3 and 4, it is disposed within a mold cavity 42, asillustrated in the lefthand portion of FIG. 5, with a male mold part 44disposed within the cavity and including a shaft 46 extending downwardlyinto the tube 14. Thereafter, a plastic hub is molded about thecup-shaped bulb portion, as illustrated in the righthand portion of FIG.5. It will be noted that the hub 46, as illustrated in FIG. 5, is moldedso that it is disposed or contiguous with both the exterior and theinterior of the bulb portion 40. That portion of the hub 46 disposedinteriorly of the bulb 40 defines a passage 48 within the bulb 40 whichis coaxial and generally of the same diameter so as to be substantiallyan extension of the inner passageway 50 of the tube 14. The hub 46includes a cavity 52 which includes a tapered lower portion 54 whichcommunicates with the passage 48.

Thus, as illustrated in FIGS. 3 and 4, the tube 14 includes an irregularend defined by the cup-shaped bulb 40 which is not conformed to theshape of the remainder of the tube 14. The bulb, as viewed in FIG. 4,has an outer periphery which is disposed at different distances radiallyfrom the axis of the tube and, more specifically, defines an ovalwhereby the end portions of the oval are disposed at greater distancesfrom the axis of the tube than are the side portions of the oval. Itwill be noted that the wall thickness of the bulb 40 is thicker than theremainder of the tube 14. Accordingly, as the wall thickness of the bulbis greater than that of the tube, the pull-off strength or the strengthnecessary to separate the tube from the hub 46 is greatly increased andto the extent that the tube portion 14 will rip, tear or separate beforethe bulb portion 40 will be separated from the hub 46. Additionally, asthe hub 46 includes a portion disposed interiorly of the bulb 40 thereis no leakage between the bulb portion 40 and the hub 46. Further, asthe bulb is oval-shaped, relative rotation between the tube 14 and thehub 46 is prevented which further increases the force necessary toseparate the two components and prevents the likelihood of leakagebetween the two components.

Although the subject invention has been described in connection with acatheter, it may be utilized with other plastic tubular members.

The invention has been described in an illustrative manner, and it is tobe understood that the terminology which has been used is intended to bein the nature of words of description rather than of limitation.

Obviously, many modifications and variations of the present inventionare possible in light of the above teachings. It is, therefore, to beunderstood that within the scope of the appended claims, the inventionmay be practiced otherwise than as specifically described.

The embodiments of the invention in which an exclusive property orpriviledge is claimed are defined as follows:
 1. An apparatus forforming a plastic tube comprising: vertically disposed mandrel forinsertion within the tube for vertically supporting the tube with theupper end of the tube disposed about said mandrel, and a pair of spacedand oppositely facing heating means for radiantly and simultaneouslyheating opposite sides of the upper end of the tube while disposed onsaid mandrel for heating said opposite sides of the tube at a higherrate than the remainder of the circumference of the tube whereby theupper end of the tube form a bulb of oval configuration upon beingheated by said heating means.
 2. An apparatus as set forth in claim 1including mandrel carrier means for supporting said mandrel and formoving said mandrel into and out of said heat zone.
 3. An apparatus asset forth in claim 2 including base means for receiving and positioningsaid carrier means.
 4. An apparatus as set forth in claim 1 wherein saidheating means defines a pair of spaced walls extending generallyperpendicular to said mandrel and heat generating means disposed betweensaid walls and spaced from said mandrel.
 5. An apparatus as set forth inclaim 4 wherein said walls include a top wall extending across the topof said mandrel and a bottom wall with a slot therein for receiving theupper end of said mandrel.
 6. An apparatus as set forth in claim 5wherein said heating means includes heat generating devices disposedbetween said top and bottom walls and spaced from the edges of saidslot.
 7. An apparatus as set forth in claim 6 wherein said slot iselongated and including a plurality of said mandrels for dispositionalong said slot whereby opposite sides of tubes disposed on saidmandrels are heated by heat radiating from said heat generating devices.8. An apparatus as set forth in claim 7 wherein said heating devicescomprise elongated resistance heaters.